1. Technical Field
The invention relates to a centrifugal multiplate clutch with a pot-type clutch drum and a rotor which shows several disk shaped plates, fixed on a motor shaft, for which respectively the hub and the centrifugal weight are connected over a rocker bar so that, when the no-load number of revolutions is considerably exceeded, the centrifugal weight is radially moved outwards and is frictionally put against the clutch drum.
The power transfer of a motor shaft of small hand-operated implements driven by an internal combustion engine mostly takes place over a centrifugal clutch to the driven shaft which is connected with the tool. The function of this centrifugal clutch is to separate the motor shaft from the driven shaft in the no-load r.p.m. range of the engine in order to guarantee an immobilization of the tool and to connect the motor shaft and the driven shaft in the load r.p.m. range of the engine with as little slippage as possible in order to allow a complete torque transfer to the tool. Especially in the transition area between these two modes of operation of the engine, undesired states appear for which, due to a slippage between the movable clutch parts and the clutch drum, it is not the full torque which is transferred to the driven shaft so that the full power of the engine is not available on the tool. Therefore, for centrifugal clutches the aim is to maintain this transition area as small as possible to be able to meet legal requirements which allow the rotation of the tool only in an upper no-load r.p.m. range as well as to avoid a slippage in the lower load r.p.m. range, to avoid mechanical as well as thermal damages of the clutch, especially of the clutch drum and the clutch bearings and to be able to transfer the desired torque to the tool.
2. Prior Art
According to the prior art, two types of centrifugal clutches are used at present. According to a first type, centrifugal segments which are maintained at no load at a distance from the clutch drum by means of retaining springs are used. By an increase of the number of revolutions, the centrifugal force of said segments exceeds the resilience of the springs so that the centrifugal segments are radially moved outwards and are frictionally put against the clutch drum. As an alternative, centrifugal multiplate clutches are used according to the prior art for which several separate disk shaped plates are put in a row on the motor shaft. For increasing the number of revolutions of the motor shaft, the centrifugal weights placed at the end of the plates are radially moved outwards until they frictionally engage with the clutch drum. Compared with the clutch working with centrifugal weight segments, the centrifugal multiplate clutch has, to begin with, the advantage of a more constant load of the clutch parts so that a deformation of the clutch drum is avoided because of several offset bearing spots of the individual plate parts. This can be achieved in particular by the offset mounting of the individual plate parts. Moreover, the clutch mounting is easier to manipulate, especially also for service cases. Finally centrifugal multiplate clutches are cheaper to manufacture because namely several congruent plates, which can be manufactured in a corresponding simplified way, can be used for the centrifugal multiplate clutch.
Multiplate clutches are used in particular for hand operated implements such as, for example, clutches for two-cycle lawn trimmers.